Method and system for operating two-and four-stroke engines using low sulfur fuels

ABSTRACT

A method for operating a two-stroke engine using low sulfur fuels. Blended cylinder oil is produced by blending base oil and at least one additive where the total base number (“TBN”) of the blended cylinder oil ranges from 1 TBN to 20 TBN. The engine is operated by supplying the blended cylinder oil and a fuel having less than 1.0% sulfur to the engine cylinders. The additive includes a low TBN calcium salts at a weight ratio ranging from 90:10 to 10:90; or any combination thereof. 
     A method for operating a 4-stroke engine using low and high sulfur fuels. Blended oil, having a TBN that is greater than 20 TBN, is produced by blending base oil and at least one additive. The engine is operated by exchanging a low sulfur fuel having less than 1.0% sulfur with a high sulfur fuel. The engine lubricating system is switched to the blended cylinder oil in accordance with switching the fuel from a low sulfur fuel to a high sulfur fuel.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/874,105, filed Dec. 11, 2006.

FIELD OF THE INVENTION

The invention relates to a method of creating blended cylinder oils foruse with low sulfur fuels.

BACKGROUND OF THE INVENTION

Two-stroke crosshead engines used in marine or stationary applicationsare equipped with two separate lubricating oil systems. One lubricatingsystem includes so-called system oil that is used in the engine crankcase for lubrication and cooling of the engine's bearings and oil-cooledpistons as well as for activation and/or control of various valves orthe like. Typical system oils usually have an SAE viscosity of about 30with a relatively low TBN content, typically below 10. These exemplaryvalues may vary dependent on the actual application and the specificdesign of the systems that the oils are used in.

The other lubricating system, of a two-stroke crosshead engine, includesan all-loss lubricant (cylinder oil) that normally is used forlubrication of the engine's cylinders, piston rings and piston skirt.Typically cylinder oil is spent continuously by each turn of the enginewhereas the system oil in principle is not spent (except by smallerunintentional leakages). The lubrication system comprising the cylinderoil is also often referred to as an “all-loss” lubrication system as theoil is spent. Cylinder oil typically contains certain additives thatfunction to reduce, minimize or neutralise the acid level of thecylinder system. Generally, cylinder oils have an SAE (Society ofAutomotive Engineering) viscosity equivalent to about 50 and normallyhave a total base number (“TBN”) of about 40 to 70 for theneutralisation of acid products produced during the combustion process.

Four-stroke, trunk piston diesel engines, however, use only a single oiltype for lubrication and cooling. Such engines are used assecondary/auxiliary or propulsion engines on ships, or in stationarypower generation or liquid/gas transmission applications. Such used oilstypically have a SAE viscosity of about 30 or 40.

The performance properties of lubricants, in both four-stroke andtwo-stoke engines, is typically measured periodically. The propertiesmay not go beyond certain limits without jeopardizing the condition ofthe oiled engine component. Ultimately, the useful properties of bothtrunk piston engine and system oil degenerate over time and resulting ineither replenished or a complete replacement of the oil. Similarly,other lubricants used on-board vessels or at stationary sites, such ashydraulic fluids, gear oils, turbine oils, heavy duty diesel oils,compressor oils and the like, do deteriorate over time, due to e.g.contamination, oxidation, hydrolysis etc. and therefore have arereplenished or changed at certain intervals.

It is desirable to operate diesel engines using low sulfur fuels toreduce sulfur emissions. In particular, it is desirable to use straightvegetable oils (“SVO”), or SVO derivatives, and other low and very lowsulfur fuels in combination with lubricants having low total basenumber. To operate diesel engines with low sulfur fuels and retainperformance at temperatures exceeding 200° C., low TBN lubricants areneeded. The present invention provides a novel approach to producelubricants having suitable TBN values for the sulfur level of the fuelused to power the diesel engine.

SUMMARY OF THE INVENTION

The present invention provides for a method for operating a two-strokeengine using low sulfur fuels. Blended cylinder oil is produced byblending base oil and at least one additive. The TBN of the blendedcylinder oil falls within the range 1 TBN to 20 TBN. The engine isoperated by supplying the blended cylinder oil and a fuel having lessthan 1.0% sulfur to the engine cylinders. The blended cylinder oil has acomposition containing a base fluid of lubricating viscosity and amixture of at least two of the following metal detergent additives: alow (or non-overbased) TBN calcium phenate; a low (or non-overbased) TBNcalcium sulphonate; a low (or non-overbased) TBN calcium salicylate, orany combination thereof, wherein the at least two additives have aweight ratio ranging from 90:10 to 10:90.

The present invention further provides for a method for operating a4-stroke engine using low and high sulfur fuels. Blended oil is producedby blending base oil and at least one additive. The blended oil has aTBN that is greater than 20 TBN. The engine is operated by exchanging alow sulfur fuel having less than 1.0% sulfur with a high sulfur fuel.The engine lubricating system is switched to the blended oil inaccordance with switching the fuel from a low sulfur fuel to a highsulfur fuel.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from andelucidated with reference to the illustrative embodiments shown in thedrawing, in which:

FIG. 1 shows a schematic block diagram of a two-stroke engine of oneembodiment according to the present invention; and

FIG. 2 shows a schematic block diagram of a four-stroke engine of oneembodiment according to the present invention

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a schematic representation of a system 100 including atleast one two-stroke cross-head diesel engine 101. The engine 101includes a first lubricating system containing system oil 102 and asecond lubricating system includes an all-loss lubricant or cylinder oil107. The system further includes used system oil conduit 103 and 109,system oil recycle loop 108 a and 108 b, waste tank 106, a fresh systemoil tank 105, separator 107, transfer line 112, blending apparatus 104,additive tank 115, fluid storage tank 116, low sulfur-fuel tank 118,high sulfur fuel tank 119 and fuel line 120, for carrying out the methodof the present invention. Fluid storage tank 116 may be used to storebase oil, trunk piston engine oil, or used trunk piston engine oil.

According to an embodiment of the present invention, a two-stroke enginemay be operated by supplying the blended cylinder oil and a fuel havingsulfur content ranging from 1.0 wt. % sulfur to 0.001 wt. % sulfur tothe engine cylinders. In one embodiment, the fuel contains sulfurcontent ranging from 0.5 wt. % sulfur to 0.001 wt. % sulfur. In anotherembodiment, the fuel corresponds to straight vegetable oil. Blendedcylinder oil having a TBN ranging from 1 TBN to 20 TBN is suitable foruse with a low sulfur fuel. Blended cylinder oil having a TBN rangingfrom 1 TBN to 20 TBN may be produced by blending base oil and at leastone additive. The additives include bases, detergents, anti-oxidants,dispersants and fiction modifiers.

Blended cylinder oil may be produced by mixing one or more additiveswith base fluid including base oil, fresh system oil, used system oil,trunk piston engine oil, or used trunk piston engine oil. In one suchembodiment, fresh system oil may be obtained from fresh system oil tank105 and transferred to blending apparatus 104 via fresh system oilconduit 110, system oil recycle loop 108 a, separator 107, and transferconduit 112. In another embodiment, base oil, trunk piston engine oil orused trunk piston engine oil may be obtained from fluid storage tank 116and transferred to the blending apparatus 104.

In yet another such embodiment, used system oil may be used to produceblended cylinder oil. The used system oil may be obtained from the crankcase section of the two-stroke engine 101, transferred to blendingapparatus 104 via used system oil conduits 103 and 108 and transfer line112. The two-stroke engine, from which the used system oil is obtained,may be tapped continuously, near-continuously or intermittently for usedsystem oil and the used system oil is replenished with fresh system oil.

The blending process produces blended cylinder oil suitable for use intwo-stroke engines operating with low sulfur fuels. In one embodiment,the base fluid has a viscosity in the range of 9 cSt to 30 cSt at 100°C. The blended cylinder oil has a composition containing a base fluid oflubricating viscosity and a mixture of at least two of the followingmetal-organic detergent additives: a low (or non-overbased) TBN calciumphenate; a low (or non-overbased) TBN calcium sulphonate; a low (ornon-overbased) TBN calcium salicylate, or any combination thereof,wherein the at least two additives have a weight ratio ranging from90:10 to 10:90. The TBN of the blended cylinder oil falls within therange 1 TBN to 20 TBN. In another embodiment, the blended cylinder oilfurther includes a metal source including metals other than calcium andtransition metals.

A metal-organic detergent additive typically has a metal to organicanion mole ratio of 1:1 for Group IA metals and 0.5:1 for Group IIAmetals. In one embodiment of the present invention, a non-overbasedmetal-organic detergent additive has a metal to organic anion mole ratioranging from 0.2:1 to 1:1 for Group IA metals and a metal to organicanion mole ratio ranging from 0.1:1 to 0.5:1 for Group IIA metals. Inanother embodiment of the present invention, a non-overbasedmetal-organic detergent additive has a metal to organic anion mole ratioranging from 0.3:1 to 0.8:1 for Group IA metals and a metal to organicanion mole ratio ranging from 0.2:1 to 0.3:1 for Group IIA metals. Inone embodiment of the present invention, an overbased metal-organicdetergent additive has a metal to organic anion mole ratio ranging from1:1 to 8:1 for Group IA metals and a metal to organic anion mole ratioranging from 0.5:1 to 4:1 for Group IIA metals. In another embodiment ofthe present invention, an overbased metal-organic detergent additive hasa metal to organic anion mole ratio ranging from 2:1 to 6:1 for Group IAmetals and a metal to organic anion mole ratio ranging from 1:1 to 3:1for Group IIA metals.

The amount of additive mixed with the lubricating oil, to create thecylinder oil, may be determined from the amount of sulfur in the fueland the TBN of the additive.

In one embodiment, the additives include detergents such as phenate,sulphonate or salicylate salts. For an embodiment where the detergentincludes calcium phenate as an additive, the calcium phenate has a TBNranging from 20 TBN to 250 TBN. In another embodiment, the calciumphenate has a mole ratio of metal to phenate ranging from 0.2:1 to 1.5:1for a Group IA metal and ranging from 0.1:1 to 0.5:1 for a Group IIAmetal. In yet another embodiment, the calcium phenate has a mole ratioof metal to phenate ranging from 0.5:1 to 1:1 for a Group IA metal andranging from 0.3:1 to 0.5:1 for a Group IIA metal.

For an embodiment where the detergent includes calcium sulphonate as anadditive, the calcium sulphonate has a TBN ranging from 10 TBN to 300TBN. In another embodiment, the calcium sulphonate has a mole ratio ofmetal to sulphonate ranging from 0.2:1 to 2:1 for a Group IA metal andranging from 0.1:1 to 0.5:1 for a Group IIA metal. In yet anotherembodiment, the calcium sulphonate has a mole ratio of metal tosulphonate ranging from 0.5:1 to 1.5:1 for a Group IA metal and rangingfrom 0.3:1 to 0.5:1 for a Group IIA metal.

For an embodiment where the detergent includes calcium salicylate, thecalcium salicylate has a TBN ranging from 10 TBN to 200 TBN. In anotherembodiment, the calcium salicylate has a mole ratio of metal tosalicylate ranging from 0.2:1 to 2:1 for a Group IA metal and rangingfrom 0.1:1 to 0.5:1 for a Group IIA metal. In yet another embodiment,the calcium salicylate has a mole ratio of metal to salicylate rangingfrom 0.5:1 to 1.5:1 for a Group IA metal and ranging from 0.3:1 to 0.5:1for a Group IIA metal.

In another embodiment, the base additives include basic salts ofalkaline or earth alkaline elements. The alkaline/earth alkalineelements may be e.g. K, Na, Ca, Ba, Mg or the like. The basic salts maybelong to the inorganic chemical families of e.g. oxides, hydroxides,carbonates, sulfates or the like.

The dispersants may belong to the organic chemical families ofsuccinimides or the like.

As discussed above, the blended cylinder oil may be used in two-strokecrosshead engines combustion engines. The creation of blended cylinderoil results from the availability of the required initial fluid and theadditives and makes this method very suitable for offshore or on-siteapplications. In one embodiment, the production of blended cylinder oilaccording to the present invention may take place on-site such as amarine vessel. In another embodiment, the production of blended cylinderoil according to the present invention may take place using off-shoreequipment or stationary plants.

Alternatively, the blended cylinder oil is based on a mixture of oilsthat continuously, near-continuously or intermittently are tapped froman existing system and where the used oils are replenished with freshoil.

As discussed above, it is desirable to operate marine vessels with fuelshaving different sulfur content. In one embodiment, the vessel operateswith a 4-stroke engine using blended trunk piston engine oil.

FIG. 2 shows schematic representation of system 200 including a 4-strokediesel engine 201 wherein the sulfur content of the fuel may be varied.System 200 further includes filters 202, 204, and 205, oil loop 203, oilcontainer 204, three way valve 206, additive tank 207, trunk pistonengine oil (“TPEO”) conduit, mixer 209, transfer line 210, optionallyholding tank 211, blended TPEO transfer line 212, low sulfur fuel tank214, high sulfur fuel tank 215 and fuel transfer line 213.

During routine operation of marine vessels, the fuels used to power theengines may be switched from low sulfur fuels to high sulfur fuels. Inone embodiment, blended trunk piston engine oil (“TPEO”) is producedthat is suitable for use in 4-stroke engines where the TBN of the TPEOdepends upon the sulfur content of the fuel. While the engine isoperated using a low sulfur fuel, TPEO having TPN values ranging from 5TBN to 20 TBN may be used as the engine lubricant. In anotherembodiment, the low sulfur fuel contains sulfur content ranging from 1.0wt. % sulfur to 0.001 wt. % sulfur. In yet another embodiment, the lowsulfur fuel contains sulfur content ranging from 0.5 wt. % sulfur to0.001 wt. % sulfur. In still yet another embodiment, the low sulfur fuelcorresponds to a Straight Vegetable Oil (SVO). When a high sulfur fuelis used, the engine is operated using TPEO having TPN values rangingfrom 20 TBN to 70 TBN as the engine lubricant. In one embodiment, thehigh sulfur fuel contains sulfur content ranging from 1.1 wt. % to 4.5wt. %. In another embodiment, the high sulfur fuel contains sulfurcontent ranging from 1.1 wt. % to 2.0 wt. %.

When low sulfur fuel is switched to a high sulfur fuel, the enginelubricating system is then switched to the blended TPEO. The blendedTPEO has a composition containing a base fluid of lubricating viscosityand a mixture of at least two of the following metal-organic detergentadditives: non-overbased or overbased TBN calcium phenate; anon-overbased or overbased TBN calcium sulphonate; non-overbased oroverbased TBN calcium salicylate, or any combination thereof, whereinthe at least two additives have a weight ratio ranging from 90:10 to10:90. In one embodiment, the TBN of the blended TPEO has TPN within therange 1 TBN to 20 TBN. In another embodiment, the TBN of the blendedTPEO has a TBN greater than 20 TBN. In yet another embodiment, the TBNof the blended TPEO has TPN within the range 20 TBN to 70 TBN.

The present disclosure may be embodied in other specific forms withoutdeparting from the spirit or essential attributes of the disclosure.Accordingly, reference should be made to the appended claims, ratherthan the foregoing specification, as indicating the scope of thedisclosure. Although the foregoing description is directed to thepreferred embodiments of the disclosure, it is noted that othervariations and modification will be apparent to those skilled in theart, and may be made without departing from the spirit or scope of thedisclosure.

In the claims, any reference signs placed between parentheses shall notbe constructed as limiting the claim. The word “comprising” does notexclude the presence of elements or steps other than those listed in aclaim. The word “a” or “an” preceding an element does not exclude thepresence of a plurality of such elements.

1. A method for operating a two-stroke engine, comprising: (a) producinga blended cylinder oil having a total base number (TBN) ranging from 20TBN to 1 TBN by blending a base oil and at least one additive; and (b)operating the engine by supplying the blended cylinder oil and a fuelcontains a sulfur content ranging from 1.0 wt. % sulfur to 0.001 wt. %sulfur to the engine cylinders.
 2. The method of claim 1, wherein thebase oil is selected from the group consisting of system oil, usedsystem oil, trunk piston engine oil, or used trunk piston engine oil. 3.The method of claim 2, wherein the at least one additive is selectedfrom the group consisting of detergents, anti-oxidants, and frictionmodifiers.
 4. The method of claim 1, wherein the fuel contains a sulfurcontent ranging from 0.5 wt. % sulfur to 0.001 wt. % sulfur.
 5. Themethod of claim 1, wherein the fuel corresponds to a Straight VegetableOil (SVO).
 6. The method of claim 1, wherein the two-stroke engine isoperated on a marine vessel.
 7. The method of claim 6, wherein saidblending is performed on the marine vessel.
 8. The method of claim 6,wherein said blending is not performed on the marine vessel.
 9. Themethod of claim 1, wherein the blended cylinder oil has a compositioncontaining a base fluid of lubricating viscosity and a mixture of atleast two of the following: a low (or non-overbased) TBN calciumphenate; a low (or non-overbased) TBN calcium sulphonate; a low (ornon-overbased) TBN calcium salicylate, or any combination thereof,wherein the at least two additives have a weight ratio ranging from90:10 to 10:90.
 10. The method of claim 9, wherein the blended cylinderoil composition has a TBN in the range of 1 TBN-15 TBN.
 11. The methodof claim 9, wherein calcium phenate has a TBN from 20 TBN to 250 TBN.12. The method of claim 9, wherein the calcium phenate has a mole ratioof metal to phenate ranging from 0.2:1 to 1.5:1 for a Group IIA metaland ranging from 0.1:1 to 0.5:1 for a Group IIA metal.
 13. The method ofclaim 9, wherein the calcium sulphonate has a TBN from 10 TBN to 300TBN.
 14. The method of claim 9, wherein the calcium sulphonate has amole ratio of metal to phenate ranging from 0.1:1 to 2:1 for a Group IIAmetal and ranging from 0.1:1 to 0.5:1 for a Group IIA metal.
 15. Themethod of claim 9, wherein the calcium salicylate has a TBN from 10 TBNto 200 TBN.
 16. The method of claim 9, wherein the calcium salicylatehas a mole ratio of metal to phenate ranging from 0.1:1 to 2:1 for aGroup IA metal and ranging from 0.1:1 to 0.5:1 for a Group IIA metal.17. A method for operating a 4-stroke engine, comprising: (a) producinga blended TPEO having a total base number (TBN) that is greater than 20TBN by blending a base oil and at least one additive; (b) operating theengine by exchanging a low sulfur fuel having a sulfur content rangingfrom 1.0 wt. % sulfur to 0.001 wt. % sulfur with a high sulfur fuelhaving a sulfur content ranging from 1.1 wt. % sulfur to 4.5 wt. %sulfur; and (c) switching the engine lubricating system to the blendedTPEO in accordance with the exchanging.
 18. The method of claim 17,wherein the base oil is selected from the group consisting of systemoil, used system oil, trunk piston engine oil, or used trunk pistonengine oil.
 19. The method of claim 18, wherein the at least oneadditive comprises at least one base.
 20. The method of claim 19,wherein the at least one base comprises basic salts of alkaline or earthalkaline elements, and/or detergents and/or dispersants.
 21. The methodof claim 17, wherein the blended TPEO composition has a TBN in the rangeof 20-70 TBN.
 22. The method of claim 17, wherein the low sulfur fuelcorresponds to a Straight Vegetable Oil (SVO).
 23. The method of claim17, wherein the 4-stroke engine is operated on a marine vessel.
 24. Themethod of claim 23, wherein said blending is performed on the marinevessel.
 25. The method of claim 23, wherein said blending is notperformed on the marine vessel.
 26. The method of claim 17, whereinblended TPEO has a composition containing a base fluid of lubricatingviscosity and a mixture of at least two of the following metal-organicdetergent additives: non-overbased or overbased TBN calcium phenate; anon-overbased or overbased TBN calcium sulphonate; non-overbased oroverbased TBN calcium salicylate, or any combination thereof.